The SurSaUD® syndromic surveillance system (Health Surveillance of Emergencies and Deaths) was established in 2004 by the French Institute for Public Health Surveillance (InVS) in the wake of the 2003 heat wave. This extreme weather event, with its severe consequences—overburdened emergency departments and excess mortality of more than 15,000 deaths—demonstrated that the surveillance systems available at the time were unable to detect such a phenomenon or quickly assess its impact on the population. The Ministry of Health then asked the InVS to establish a surveillance system that was both non-specific (not based on pre-identified pathologies) and reactive, with real-time data reporting. The SurSaUD® system was thus developed with the aim of detecting new threats to public health (whether infectious or environmental, natural or malicious) but also to monitor and assess the impact on public health of known and expected events (seasonal epidemics) or unexpected events (industrial disasters, extreme weather events, etc.). This system, which relies on close collaboration between InVS epidemiologists and healthcare professionals in the field, is one of the tools that enables the Institute to carry out, on a daily basis and at both the national and regional levels, the health monitoring, surveillance, and alert missions entrusted to it. Four sources of relevant, responsive information capable of providing daily updates on the population’s health status feed into the SurSaUD® system: - hospital emergency departments (EDs) within the OSCOUR® network; - the SOS Médecins association of private emergency physicians; - mortality data transmitted by INSEE; - electronic death certificates. (R.A.)